Beijing temporarily shut down 103 heavily polluting factories and took 30% of government vehicles off roads to combat dangerously high air pollution, state media reported on Tuesday, but the capital's air remained hazardous despite the measures.

Green schemes to fight climate change by producing more bio-fuels could actually worsen a little-known type of air pollution and cause almost 1,400 premature deaths a year in Europe by 2020, a study showed on Sunday.

Private investors may be allowed to earn carbon credits by paying poor countries to halt the destruction of tropical forests, but a U.N. climate summit failed to agree the details needed to get the ambitious programme off the ground.